Partial identification of the mab _CDAmp1 antigen at the epithelial–mesenchymal interface in the developing kidney

Abstract.

The nature of the primary functional events of nephron induction is still unknown, making it impossible to completely understand the mechanism of tissue interaction between collecting duct ampulla and the surrounding nephrogenic mesenchyme. Soluble morphogenic substances are known to be exchanged in the process and it is assumed that nephron induction requires close contact between both tissues involved. Contrasting with that assumption our previous investigation revealed a thick fibrous meshwork separating nephron inducer and mesenchyme. Our present investigation focused on the molecular characterization of the mab _CDAmp1 antigen, which is found only in this meshwork. The protein was shown immunohistochemically to be located exclusively at the embryonic collecting duct ampulla and could be clearly distinguished from other extracellular matrix proteins such as collagen type IV, laminin, reticulin, and fibronectin. Two-dimensional electrophoresis of the soluble form of P_CDAmp1 showed a molecular weight of 87,000 and an isoelectric point of 4.3–4.4. Results from N-terminal sequencing indicated a partial sequence homology of P_CDAmp1 to collagen type IV α2-chain precursor but additionally yielded unknown sequences. Thus P_CDAmp1 is a novel, collagen-related protein, restricted to the fibrous meshwork at the mesenchymal–epithelial interphase, which is the site of primary epithelial–mesenchymal interaction.